This invention relates generally to a process for converting organic material into a usable embrittled material and more particularly to a process for increasing embrittlement efficiency and reducing the energy required to grind the embrittled material to a finely divided form.
Conservation of natural fuel resources and the disposal of organic solid waste materials have become increasingly severe problems in view of increasing population. Disposal is a significant problem in urban and suburban areas and in the increasing number of industries generating solid organic waste. The large fraction of these organic wastes are combustible and is made up of such materials as paper, textiles, leather, rubber, yard waste, wood waste and bark, garbage and various forms of plastics. One embodiment of the process of the invention is directed to the conversion of these combustible materials making up the organic fraction of solid wastes into a finely divided product which is currently being used as a fuel or fuel supplement.
In U.S. Pat. Nos. 3,961,913 for Process For Treating Organic Wastes And Products Thereof and U.S. Pat. No. 4,008,053 for Process for Treating Organic Wastes, both in the names of Richard S. Brenneman and John J. Clancy and assigned to the same assignee as this application, there is described and claimed a process which makes it possible to treat the organic fraction of solid waste and cellulosic material to form a finely divided, relatively dense fuel material or fuel supplement using a relatively small amount of energy. The resulting product is a finely divided material usable as a fuel or fuel supplement in existing combustion equipment without requiring substantial modification. This product retains essentially all of the dry weight and caloric content of the original waste material from which it is formed. The specification of each of these issued patents is incorporated herein by reference.
In the process described in these issued patents, the material to be embrittled is treated with one or more mineral acids and heated to an elevated temperature under conditions to form an embrittled material. This embrittled material is readily reducible to a finely divided form, without effecting any substantial pyrolysis, decomposition or loss in dry weight of the organic waste. The process may also include the steps of separating organic and inorganic fractions, of primary gross size reduction and predrying before embrittlement and grinding, separating the fuel product from inorganics, pelletizing and mixing with other fuels subsequent to embrittlement.
Embrittlement occurs by treating the organic fraction of solid waste or cellulosic material with acid. The embrittled material is then subjected to a grinding step using, for example, a tumbling device such as a ball mill. Since the organic material is embrittled, relatively less energy is required for grinding than grinding an untreated solid organic fraction of waste or cellulosic material to the same degree of fineness. This factor is one of the principal energy conserving aspects of the process of the patented inventions. Further reduction of this energy required for grinding the embrittled material would make the processes of these patents even more attractive from both an economical and ecological point of view. In addition, any reduction in the temperatures required for the embrittlement would also increase the attractiveness of the embrittlement process. Accordingly, it is desirable to provide an embrittlement process which provides an improved degree of embrittlement, increased grinding efficiency and allows a reduction in embrittlement temperature in the above-described process for treating the organic fraction of solid wastes and cellulosic material.